During the construction of buildings, it is often necessary to transport and position heavy and awkward objects, such as pipes, beams, or the like. In some cases, a crane provided with a telescoping crane boom is well suited to accomplish the task, particularly where a motorized head has been placed on the end of the telescoping crane boom to afford rotational movement of the load about a longitudinal, generally fore and aft axis centered on the boom's end. However, even though motorized heads have added flexibility to the rather limited movement afforded by telescoping crane booms, limitations still exist.
The main limitation stems from the fact that the customary load or work piece is rigidly secured in a position such that its long dimension is perpendicular to the longitudinal axis of the telescoping crane boom. Since the longitudinal axis of the load cannot be changed with respect to the longitudinal axis of the crane boom, even though the boom is provided with a motorized head, forward movement of an elongated load into a narrow passageway, for instance, cannot be effected.
The present invention overcomes the deficiencies of the prior art by including an intermediate sub-frame between the main frame and the support framework. The sub-frame can pivot with respect to the main frame and the support framework can rotate with respect to the sub-frame in such manner as to permit the longitudinal axes of the telescoping crane boom and that of the load to be brought into parallelism. Hydraulic motors are preferably used to effect pivoting and rotation, thereby affording a nice degree of control and any desired alignment of the work piece.